What is foreshadow by the appearance of tybalt what is the effect of his appearance on benvolio ,mercutio, and audience

The appearance of Tybalt foreshadows Romeo's eventual death as he narrowly escapes it at Tybalt's hands. It creates a sense of impending danger for Benvolio, Mercutio and the audience as it is the first indication that Romeo is doomed. I hope this helps.

I could not understand what you were asking, however I hope that my answer is helpful to you.

ANSWER
Romeo returns to the Capulet gardens and overhears his friends making fun of him (Mercutio and Benvolio - who still believe he is lovesick over Rosaline). They leave and he begins to speak of his feelings for Juliet. Then he overhears her saying she would be willing to profess her love and no longer be a Capulet if only she knew Romeo felt the same. Overhearing this, Romeo does profess his love for Juliet. She wants to make sure his feelings are true. The nurse interrupts their conversation several times before they agree that Juliet will send someone to Romeo the next day to learn of the plans of when they shall wed. In the meantime, Romeo leaves in search of a monk to marry them.

The best answer is b: she could search for an author or a list of sources that is how she can know it is credible.